Electrocatalysts driving the hydrogen evolution reaction (HER) are vital for advancing electrocatalytic water splitting and sustainable hydrogen production. This work presents the optimized synthesis of binder-free NiCoP layered double hydroxide (LDH) nanocomposites (NCs) through a one-step electrodeposition process, systematically tuning deposition potential, time, and transition-metal concentration. Raman analysis of NiCoP LDH deposited at −1 V vs SCE for 20 min in 0.3 M transition-metal solution reveals new vibrational features, while XPS shows a negative binding-energy shift, indicating enhanced electronic coupling and charge redistribution within the NiCoP LDH NCs. These effects accelerate charge transfer and improve interfacial kinetics compared to NiP and CoP analogues. Electrochemical evaluation demonstrates outstanding HER activity, delivering 200 mA cm⁻² at an overpotential of 141 mV, exhibiting a Tafel slope of 46 mV∙dec⁻¹, and maintaining durability over 50 h at 100 mA cm⁻². In a full cell electrolyzer, pairing NiCoP LDH with FeNiS@FeS LDH nanoflowers achieves 10 mA cm⁻² at 1.61 V and sustains stable operation for 50 h at 20 mA cm⁻². These findings highlight the critical role of electrodeposition optimization in tailoring NiCoP LDH NCs and guide the systematic development of high-performance transition-metal catalysts for efficient water splitting and clean-energy applications.